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Path: sserve!newshost.anu.edu.au!harbinger.cc.monash.edu.au!msuinfo!gmi!usenet.eel.ufl.edu!usenet.cis.ufl.edu!eng.ufl.edu!spool.mu.edu!howland.reston.ans.net!math.ohio-state.edu!hobbes.physics.uiowa.edu!newsrelay.iastate.edu!news.iastate.edu!soclab.soc.iastate.edu!flipk From: flipk@iastate.edu (Phil Knaack) Newsgroups: comp.os.386bsd.bugs Subject: Re: aha0: DMA beyond end of ISA Date: 20 Sep 94 21:09:34 GMT Organization: Iowa State University, Ames, Iowa Lines: 33 Distribution: comp Message-ID: <flipk.780095374@soclab.soc.iastate.edu> References: <KSTAILEY.94Sep19183504@leidecker.std.com> NNTP-Posting-Host: soclab.soc.iastate.edu In <KSTAILEY.94Sep19183504@leidecker.std.com> kstailey@leidecker.std.com (Kenneth Stailey) writes: >When I raise the core memory (RAM) from 16MB to 20MB I get: >aha0: DMA beyond end of ISA >error messages. >Why does this happen? Is there anything that will fix this? This happens when the buffer for I/O is beyond the range of addresses accessable by ISA. 16 meg should be okay, but some motherboards allow you to reclaim the "lost" 384k (from I/O addresses A0000-FFFFF) and put it just beyond the end of the rest of the memory, so you actually get a tad more than 16meg. Was your IDE controller a VL Bus controller? Then it would be able to reach all of this memory. Or maybe the wd driver just doesn't check? The fix is bounce buffers. Has anyone done this for the aha driver? Either turn off the reclaiming of the extra memory (most motherboards that do this allow you to disable it), hack machdep.c to force the physical memory used to 16M (anyone got a specific patch for this?), or use a 32 bit bus (EISA, VL or PCI) controller. >Ken Cheers, Phil -- Phil Knaack flipk@iastate.edu WGA, Sociology Department flipk@cs.iastate.edu Iowa State University flipk@vorpal.com